1. Field of Invention
The invention relates to a hybrid vehicle drive control apparatus and a hybrid vehicle drive control method as well as a program thereof.
2. Description of Related Art
A known vehicle drive apparatus installed in a hybrid vehicle for transferring a torque of an internal combustion engine, that is a portion of the engine torque, to an electric generator (generator-motor) and transferring the rest of the engine torque to driving wheels is provided with a planetary gear unit that includes a sun gear, a ring gear and a carrier. The carrier is connected to the engine. The ring gear is connected to the driving wheels and to a vehicle drive electric motor. The sun gear is connected to the generator. Rotation output from the ring gear and the vehicle drive electric motor is transferred to the driving wheels, thus generating a vehicle-driving force.
If, in this kind of vehicle drive apparatus, the rotation speed of the generator (i.e., generator rotation speed) is relatively low, the electric power consumption increases and the electric power generation efficiency of the generator decreases. As such, the fuel economy of the hybrid vehicle correspondingly degrades. Therefore, if the generator rotation speed is relatively low, a generator brake is engaged in order to stop the generator (shut down) (Japanese Patent Application Laid-open No. 9-156387).
To that end, a generator control device of the vehicle drive apparatus executes a generator rotation speed control in order to set a target generator rotation speed, that is a target value of a generator rotation speed, at zero (0). The control also causes the generator to receive the engine torque and then engage the generator brake. Subsequently, the generator control device instantaneously changes the torque of the generator, that is the generator torque, to zero to stop the generator.